Aerobic fitness, the ability to sustain endurance type work for prolonged periods, is the major factor in physical fitness. This capacity is usually expressed in walking, running, swimming and related activities and is determined by the measurement of maximum O.sub.2 uptake (Vo.sub.2 max). Two aspects of Vo.sub.2 max are important: absolute Vo.sub.2 max, the maximum amount of oxygen that one is able to consume during the performance of maximal work, expressed in liters/minute of oxygen (1/min); and relative Vo.sub.2 max, which is the absolute Vo.sub.2 max divided by body weight and expressed in milliliters of oxygen per body weight per minute (ml/kg.multidot.min). Absolute Vo.sub.2 max represents fitness where body weight is not a factor in performance such as during swimming, lifting, cycling, and the like. Relative Vo.sub.2 max represents fitness where body weight is lifted during performance such as in walking, running, hiking and the like. There is a large body of knowledge showing that Vo.sub.2 max is positively related to good health and longevity. A direct determination of Vo.sub.2 max, however, requires an expensive laboratory setting and is beyond the reach of most persons.
During the past half century, several attempts have been made to predict endurance fitness in adults. These early tests were based on heart rates that were manually recorded during recovery from a standard exercise, which were very inaccurate and did not include any standards. Later tests considered work load and heart rate for the prediction of Vo.sub.2 max, and this has remained the basis for all such tests. The physiological basis for the latter tests is simple: mechanical work load is proportional to oxygen uptake (energy expenditure), with little variability. Mechanical work load can easily be determined when performing on a bicycle ergometer (it equals the resistance to cycling); in an uphill walk or run on a treadmill (height to which body weight is lifted), or in stepping where work load is determined as in an uphill walk. Thus, oxygen uptake can accurately be determined by the performance of the above types of work. It is also known that heart rate increases linearly with an increase in oxygen uptake. If heart rate is recorded during at least two different work loads, and the former is plotted against the latter, a best fit straight line is drawn through these points and an extrapolation is made to the assumed maximal heart rate of the individual, which is age related. This point corresponds to the Vo.sub.2 max of the individual. Thus, low heart rates recorded during the submaximal loads indicate a high Vo.sub.2 max, while high heart rates indicate a low Vo.sub.2 max.
The most famous test for Vo.sub.2 max prediction was presented by .ANG.strand I (aerobic work capacity in men and women with special reference to age. Acta Physiol. Scan. 1960; 49, Supp. 196). The test consisted of exercising at one load on a bicycle ergometer and then measuring the heart rate after 5 or 6 minutes. Correlation tests conducted on a large number of men and women showed good correspondence with Vo.sub.2 max determined directly. The disadvantages of this test are similar to those of other tests of the same category. It is necessary to perform at least five minutes of strenuous work to determine equilibrium heart rate since it takes at least five minutes for the heart rate to level off at a particular submaximal work load. This method of determining the equilibrium heart rate has several other disadvantages: it is strenuous for most people; the presence of a specialized stationary bicycle ergometer is necessary; the fitness scores are based on only a Swedish population that may not apply to other populations; and the test is applicable to adults only.
Other tests for the prediction of Vo.sub.2 max, where more than one work load is performed, are more accurate than the .ANG.strand test. Computerized systems are now available, using bicycle or treadmill ergometers. The operator exercises at three different work loads, and the computerized system calculates the work loads, monitors the heart rates, plots the latter against the former, and extrapolates to the load corresponding to the age-dependent assumed heart rate. Oxygen uptake at that load is the Vo.sub.2 max of the individual. An example of such a system is described in U.S. Pat. No. 4,408,613 issued to Relyea, R. D. The disadvantages of the computerized Vo.sub.2 max prediction systems are: at least ten minutes of strenuous exercise are required. Adequate rest is required between the exercise periods for accurate heart rate determination, availability of expensive and stationary equipment, lack of universally accepted Vo.sub.2 max standards and the tests are applicable only to adults.
A major additional disadvantage of all the Vo.sub.2 max prediction tests discussed above is that they are designed for a general Vo.sub.2 max status prediction, for instance, their purpose is to determine Vo.sub.2 max of an individual at a particular time period in his/her life. It is not possible to perform multiple determinations. The reason for this is that all the above tests require the individual being tested to go to a specific location, wear gym clothes, and perform strenuous exercise, which is inconvenient and very difficult to do for most people, even if expense is not considered.
The Vo.sub.2 max status determination is important for general health information, to monitor progress achieved during a training program, or for athletic screening. Existing tests can, at best, inform users about their aerobic capacity on each given day. But even for this purpose, this information is largely theoretical if the results are to be used to predict performance capabilities on that day, since taking any of these tests induces fatigue. Thus, a very important health/fitness related test has not been available: a test allowing a quick estimation of aerobic capacity in a similar manner to the determination of body weight or blood pressure. It should be noted that the minimum frequency in which the determination of the latter functions are of interest (except in emergency conditions) is on a daily basis, while hourly, or a multi-daily fitness determination could be of great interest to millions of people engaged in work, exercise and sports, athletic competition, recreational pursuits and military activities.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention however, the following U.S. patents were considered related:
______________________________________ U.S. PAT. NO. INVENTOR ISSUED ______________________________________ 4,463,764 Anderson, etal 7 August 1984 4,450,527 Sramek 22 May 1984 4,408,613 Relyea 11 October 1983 3,675,640 Gatts 11 July 1972 ______________________________________
The Anderson et al patent discloses a cardiopulmonary exercise system for real time breath-by-breath acquisition, analysis, display and printing of an individual's physiologic parameters. The system includes a microprocessor based waveform analyzer that receives inputs from a CO.sub.2 analyzer, an EGG monitor, an O.sub.2 analyzer and a pneumotachograph. The waveform analyzer provides output data to a host CPU to which a CRT display or hard-copy printer may be connected to provide the medical data for assessment of an individual's heart and lungs.
The Sramek patent discloses a noninvasive continuous cardiac output monitor and a method using electrical bioimpedance measurements to monitor parameters associated with blood flow in a segment of body tissue. The invention eliminates the effect of respiration from the thoracic impedance as a function of time to provide a continuous signal indicative of pulstile thoracic impedance changes. The produced impedance signal is processed to produce signals indicative of the ventricular ejection time and the maximum rate of change of pulsatile thoracic impedance. This change is used in a microprocessor to calculate the volume of blood pumped per stroke according to an improved systolic upstroke equation.
The Relyea patent discloses an interactive exercise device that utilizes an exercise bicycle wherein wheel speed and force are monitored. An electromagnetic brake is adjusted by a control apparatus to relate the measured force to the required force. The electromagnetic brake controls the drag to implement a selected exercise program that paces the user through a specified load for a specified interval. The work load can be varied in any manner to achieve a desired exercise program. The program is recorded on a video cassette. On playback, the cassette provides the video for the monitor that is viewed by the user.
The Gatts patent discloses an apparatus for dynamic health testing, evaluation and treatment comprising the recordation of test data from large numbers of individuals to establish dynamic physical performance norms for patients of many varied types. Historical data is taken from a patient which, in conjunction with a physical examination, is used to establish a specific theoretical dynamic physical performance norm for that particular patient and the recommended loading for the dynamic health testing machine. The patient is placed on the exercise machine which is under a programmed load based upon the basic data and numerous parameters of the patient's state of health are monitored under dynamic conditions. The monitored information is continuously fed back to correct the programmed load to protect the patient against overstress. The patient's performance is then compared with his own theoretical norm and treatment is recommended consistent with the patient's age and health which would lead toward the achievement of the dynamic physical performance norm.